I think that I may have gone thru the numbers a little fast on my last blog regarding electric cars so this time I am go a little slower and show more numbers. Read on.
Much of the data on electric cars is misleading because it does not explain "duty cycle" very well. If you start with a cold electric motor, you can put several times the amount of amp's thru it and generate several times it's "continuous" horse power rating. That is why electric cars are so impressive in short races or how fast they can get to 60 mph. The problem is that an electric motor will get hot and thus has to run slower for continuous duty. Example, pulling a trailer up a long steep grade. If you were to try, the motor would over heat. People need to focus on the continuous performance rather than a 10 second burst from time to time.
The power needed to drive a car down the road is a function mostly of weight and speed no mater what kind of energy source you are talking about. For the record, electric cars are heavier than gas cars of the same capacity. Cost is also a function of the weight of the car so heavier cars cost more than light weight cars. That is a fact. The energy needed to build the car is also a function of weight and price and here again electric cars cost more and consume more energy to build and thus generate more waste in the form of Carbon Dioxide. I do not have good numbers on this but it is clear and one needs to take into account the energy necessary to build the car as well as the energy needed to operate it. One final point in this area is that the efficiency of electric cars declines over time as well as solar collectors that produce electricity. Both of these factors are over looked by most promoters of electric cars.
Here are some of the numbers that I will be using. I got these off the internet.
(1) In the USA we produce 0.85 pounds of Carbon Dioxide to produce 1 kwh of electricity
(2) In California the retail price of electricity is $0.20/kwh as of 2021. It is higher now
(3) Theoretically 1 horse power is equal to 0.7457 kw
(4) The efficiency of a DC motor/battery system is between 70-85% under normal load
(5) Lead acid batteries are the most efficient and decline over time.
I am going to calculate the true cost of running a car at 50 mph for one hour where both need to produce 40 hp. In the case of the gas car it is easy to prove by checking the gas mileage. It is not so easy for the electric car that is just one reason to be cautious about the electric car numbers. We are looking for two numbers here, (1) True cost per mile (2) Carbon Dioxide produced per mile by both types of cars.
First the electric car:
(.40hp x .75kwh x $0.20) / (.70 eff x .95 eff x 50 miles} = $0.18 //mile
Now for the gas car:
( $4.10/gal / 33 mpg) = $0.12 / mile
It seems clear that gas cars cost less per mile than electric cars.
Now for the Carbon Dioxide:
First the electric car.
(0.85#/kwh x .75 kw/hp X 40 hp ) / (.70 eff x ,95 eff x 50 miles) = 0.81#/mile
Now for the gas car"
(19.64#/gal / 33mpg) = 0.595 #/mile
From my numbers the electric car produces more Carbon Dioxide per mile than does the gas car by 24%. How can that be, you may ask? My Subaru is lighter and gets 33 mpg. For the gas car to be equal to the electric it would have to only get 24 mpg. I think that is about the national average.
For the gas car to cost as much per mile as the electric car it would have to only get 22.8 mpg. It seems to me that there is a bigger pay off from increased mileage for gas cars than switching to electric. Next time I am going to get into this whole ethanol business. It seems that there is a lot there that is not being reported or understood my the voters.
I hope that you can follow my calculations this time.
PS--I did not take into account the car heater or the loss of charge while your car is siting in the garage or in the airport parking lot nor poor performance during cold weather. It gets even worse. How about the time to charge your battery compared to the time to fill your tank? What if you live in an apartment that only has a 100 amp service? What then?
